Such a device is known from the document US 2005/0224196 A1, the entire contents of which are herewith part of this application because of the reference. In this case, an axial guide is used, which comprises a groove embedded into the essentially cylindrical circumferential surface of the axis segment. For producing the axial guide, a tongue, which is associated with the mounting element, meshes with the groove, as a result of which the position of the mounting element is fixed in the axial direction to the axis segment. Here, the tongue is designed as being shorter than the associated groove.
In practice, the tongue is used not only for producing the axial guide, but at the same time also for locking the mounting element in preset rotation positions in relation to the axis segment. For this, locking recesses are provided in the end areas of the groove for locking the tongue.
The drawback here is that the tongue, which is designed as comparatively short, can be sheared off relatively easily. Consequently, a reliable operability cannot be guaranteed. In addition, two grooves deviating from each other in their arrangement must be inserted into the axis segment for preparing a selective left-sided or right-sided mounting of the device or of the window blind end piece. The tongue is attached to the mounting element, such that the mounting element is suitable for a left-sided mounting in a first position in relation to the axis segment. For a right-sided mounting, the mounting element must be brought into a second position different from the first position in relation to the axis segment and mounted. The drawback here is that, for example, in the case of an at first incorrect mounting of the mounting element at the axis segment, the mounting element must first be removed, rotated and then mounted again in the correct position for the desired mounting. There is consequently the risk of a premature wear and/or shearing off of the tongue, as a result of which the operability of the device is compromised.